1. Field of the Invention
The present invention relates to a display system and more particularly to a radar and navigation chart real time simultaneous display system.
2. Description of the Prior Art
Normal ship mounted radar displays continuously show the moving ship in the center of the radar display screen and the above surface fixed objects move on the radar display screen with respect to the fixed ship. Therefore, when a ship is cruising near the shore the radar will continuously show the ship in the center of the radar screen and the land terrain will be continuously moving.
For purpose of improved navigation it is desirable to present a radar display wherein the terrain remains fixed and the moving ship is displayed as a moving ship and not stationary in the center of the radar screen. This is achieved by conventional navigational computers that are responsive to the ship's bearing sensor (gyro), the ship's speed sensor, and the ship's radar signal and produces the above described processed slewed radar signal. This provides a useful display but the display does not include much of the information that is included on a navigation chart such as the water depth contours. Therefore, it is necessary for the ship's captain to be in continuous verbal communication with the navigator, who has the navigation charts, regarding the water depth of the planned course as shown by the water depth contours on the navigation maps. This procedure is adequate for many navigation operations. However, in situations where the ship is moving rapidly in coastal or river waters it is not generally adequate since it is very difficult to rapidly communicate the water depth, navigational markers, and the like in the vicinity of the planned course by the navigator to the captain.
The present invention overcomes this problem by continuously displaying on a TV screen both the processed slewed radar information and the navigation chart information for immediate visual use by the ship's captain.